Chemical process for the etching of rubber principally for the obtention of impression prints



Patented Jan. 18, 1927.

UNITED STATES PATENT OFFICE.

ETIENNE SARDOU, 0F MAR SEILLES, FRANCE.

CHEMICAL PROCESS FOR THE ETCHING OF RUBBER PRINCIPALLY FOR THE OIBTENTION OF IMPRESSION PRINTS.

No Drawing. Application filed September 29, 1925,

This invention relates to a process of etching rubber, the object of the invention being to provide a chemical process by means of which non-porous impression sheets which will not swell in use and which can readily be engraved to the required depth in a few minutes are provided.

I am aware that attempts have been made to engrave rubber prints by the use of a fatty acid and also b burning or cutting the design into the rub er by the use of very sharp blades. These operations, however, not only consume considerable time and are therefore expensive, but the prints thus obtained must be retouched, since they cannot be finished by the use of fatty acids and are weak and porous, because the fatty acid softens them so that when colors containing oil and varnish are applied thereto the prints are destroyed. Attempts have also been made to produce prints by vulcanizing a rubber sheet in a mold. This method, however, requires the use of a metal original engraved in relief, and the rubber must be vulcanized for each print.

In carrying out the present invention, the rubber sheets or foils may be prepared according to any of the usual methods, and may be composed of rubber, sulphur and any suitable filling material. The filling material, however, must be such that it will not hamper the chemical process, and silica-com taining or fat-containing fillings must be avoided. The rubber sheet or foil is then vulcanized on to a sheet of paper which has been rendered moisture-resisting by being saturated with a fatty substance, or reinforced by the incorporation therein of threads all running in the same direction.

After the usual normal vulcanization is completed, the sheet must be superficially.

super-vulcanized in order to eliminate porosityand the liability of swelling, and also to increase the polish without destroying its elasticity. This may be accomplished, for instance, by the action of ultra-violet rays, or by the action of sulphur chloride, etc.

The transfer of the designs on to the rubber sheets may be accomplished in any well known manner, for instance, by drawing the same directly thereon, or by lithographic transfer or photography. The sheet is then covered with an impalpable stratum of fatty and resinous substances, such for instance covered Serial No. 59,438, and in France October 15, 1924.

as yellow wax, Palestine bitumen, or the like and the surface is wiped so that the impalpable powder adheres only on the lines of the design, whereupon the sheet is heated to the melting point of the substances forming the coating. The sheet is then engraved or etched by bringing the rubber surface thus prepared into contact with a mixture of the following ingredients:

Nitric acid (36) 50 centigrammes Potassium bichromate 2 to 5 rammes The surface of the rubber is sub1ected to a water solution of the above ingredients for about ten minutes, whereupon all of the unparts will be etched, leaving in relief only the covered parts. After this preliminary engraving, the sheet is rinsed in acetone or alcoholic soda to dissolve the remaining nitrated rubber. tained is usually not sufficiently deep for printing purposes. The etching may be completed in thefollowing manner: a

The sheet is stretched on a smooth metal cylinder and is inked by means of an equally smooth inking roller. Ink will be collected only on the portions in relief, but b exerting some pressure on the roller the ink will be forced also into the depressions. The sheet is again covered with an impalpable stratum of material as hereinbefore described, again wiped and subjected to the acid bath.

Prints prepared as above described may be mounted on metal rollers of rotating printing machines and inked by mean of perfectly smooth inking rollers. It is to be understood that the etching process herein described is equally applicable for etching rubber for any purpose whatsoever.

Having thus described my invention, what I "claim is:-

'1. The process of etching rubber sheets which consists in subjecting said sheets to a superficial supervulcanization, reproducing the desired design thereon, covering the lines of said design with an impalpable pul verulent mixture of fatty and resinous substances, and subjecting the surface of the sheet to tl1e action of a solution of nitric acid and potassium bichromate.

2. The process of etching rubber sheets which consists in subjecting said sheets to a superficial supervulcanization, reproduce ing the desired design thereon, covering the The first etching ob subjecting the surface of the sheet to the eelines of said design with an impalpable pultion of a solution of nitric acid and potasverulent mixture of fatty and resinous subsium bichromate. stances, subjecting the surface of the sheet 4. The process of etching rubber sheets to the action of a solution of nitric acid and which consists in subjecting the same to a 20 potassium bichromate, rinsing the sheet in superficial snpervulcanization, reproducing acetone, inkin the desi n, and repeating the the desired design thereon, covering the lines treatment wit fatty an resinous substances of said design with an impaipable pulveruland with the solution of nitric acid and poent mixture of fatty and resinous substances, tassium bichromate. and subjeetingthe surface of the sheet to 25 3. The process of etching rubber sheets the action of a solution containing nitric acid which consists in subjecting the same to the of 36 concentration and potassium bichroaction of ultra-violet rays, reproducing the mate in the approximate proportions by desired design thereon, covering the lines of weight of and 2-5. 4 said design with an impalpable pulverulent In testimony whereof I'have signed my 30 mixture of fatty and resinous substances, and name to this specification. I

ETIENNE SARDOU. 

